Most commercial DJ applications (e.g. Serato, Virtual DJ, Traktor) can be controlled by means of keystroke commands from the computer's alphanumeric keyboard, and/or by means of MIDI (Musical Instrument Digital Interface) commands from an external source or from a “virtual” MIDI source running as a software application within the same computer. Some third-party software is also tightly integrated with custom hardware and sold as a package. Game players also control video games by keystroke commands from the computer's alphanumeric keyboard.
In each case, a particular keystroke controls a dedicated function, and the user enters numerous keystrokes during a performance or play. With respect to DJ applications, MIDI control messages are created by activating respective switches such as tactile push-buttons, switches and knobs, where each switch controls a dedicated MIDI control message. As DJ applications and video game applications continue to increase in performance and complexity, the user is increasingly challenged to master the respective controllers and functions to create appealing and successful performances. With enough time and practice, users build their skills.